Compressed gas actuated electrical switch having contacts maintained closed by gas pressure and opening damper means



Aug. 1967 J. SCHNEIDER ETAL 3,339,045

COMPRESSED GAS ACTUATED ELECTRICAL SWITCH HAVING CONTACTS MAINTAINED CLOSED BY GAS PRESSURE AND OPENING DAMPER MEANS Filed Dec. 7, 1964 38- Fig.2

INVENTORS Josf Schneider United States Patent t... I a-M 5. COMPRESSED GAS ACTUATED ELECTRICAL QSWITCH HAVING CONTACTS MAINTAINED CLOSED BY GAS PRESSURE AND OPENING DAMPER MEANS Jost Schneider, Baden, and Dieter Floessel, Fislisbach, Switzerland, assignors to Aktiengesellschaft Brown, Boveri & Cie., Baden, Switzerland, a joint-stock company of Switzerland Filed Dec. 7, 1964, Ser. No. 416,393 Claims priority, application Switzerland, Dec. 20, 1963, 15,760/63 6 Claims. (Cl. 200-148) This invention relates to electrical power switches i.e. circuit breakers and more particularly to an improvement in circuitbreakers of the gas blast type including a stationary pin contact member and a movable nozzle contact member forming a pressure contact, the movable contact member including at its nozzle end a drive piston which is subjected temporarily to the action of a pressurized gas when it is desired to open the circuit breaker contacts.

Gas blast circuit breakers of the type referred to are known and in which a strong spring is used to bias the movable nozzle contact member into engagement with the stationary contact member. The contact members are normally closed by the force exerted by this spring and the spring force is overcome temporarily by the pneumatic force of the pressurized gas acting against the drive piston part of the movable contact member when the circuit breaker is to be opened. As the contact members separate, the are created by the load current being interrupted is blown through the nozzle and extinguished. After arc extinction, an isolating switch in series with the contacts of the circuit breaker is opened, and thereafter the contacts of the circuit breaker are permitted to reclose by the biasing force stored in the spring when the pressurized gas is cut off.

from the circuit breaker.

A circuit breaker with this type of actuating mechanism must necessarily use a very strong biasing, i.e. reclosing spring force, in order to be at least equal in the closed position of the contacts, to contact separating forces which are produced by the electrodynamic elfects of very high currents e;g. short circuit currents passing through the circuit breaker. Otherwise, the contacts would be forced apartIt has accordingly been necessary to utilize spring forces up to some hundred kilopond in order to keep the contacts closed under this condition. Moreover, mechanical abutment dampers are required in the known constructions to limit the switching stroke of the movable contact member and these tend to make the movable contact member vibrate when in the open position.

The general object of this invention is to provide an improved circuit breaker construction which eliminates the disadvantages which have been referred to. In particular the improved construction substitutes a pneumatic biasing force for the strong spring biasing force previously used to reclose' the contacts, this pneumatic force being exerted continuously and being derived from the same source as is used to supply pressurized gas to the drive piston part of the movable contact member so that as the gas pressure at the drive piston decreases so also will the counter applied pneumatic reclosing force decrease and hence, enable'the contact members to be kept open even in cases where the gas pressure drops to .a very low value. This would not be possible in the case where the contact reclosing force is established by a biasing spring which has a constant force characteristic.

*The'pneumatic counter force for continuously biasing the circuit breaker contacts towards their closed position is preferably established by a second piston part on the ,2 movable contact member having an effective surface area less than that of the drive piston part so as to establish a continuous counter, reclosing force but which is always less than the force applied to the drive piston part when it is desired to open the contacts. Since both piston parts are subjected to the same source of pressurized gas, the pressure drop at the source, e.g. a reservoir, when gas is admitted to the drive piston part has no adverse effect even in the case of a comparatively large drop in pressure and hence, enables one to utilize a comparatively small sized reservoir for the pressurized gas. This would not be possible in the case of a circuit breaker construction utilizing a strong spring for reclosing the contacts since the spring force Would cause premature reclosure of the contacts in the event of a rapid drop in the gas pressure which would tend to take place in a small sized reservoir.

The second piston part on the movable contact member preferably operates within a cylinder which is at .all times in communication with the pressurized gas reservoir, and located within this same cylinder is a damper piston adapted to be actuated by the movable contact member, and also comparatively light springs which function principally for setting the movable contact member and damper piston to their starting positions.

The foregoing as well as other objects and advantages inherent in the invention will become more apparent from the following detailed description of one suitable embodiment thereof and from the accompanying drawings wherein:

FIG. 1 is a view in vertical central section of the improved circuit breaker with the contact members shown in the normal closed position; and

FIG. 2 is a view similar to FIG. 1 but showing the contact members in their temporary open position.

With reference now to the drawings, the circuit breaker is seen to include a main cylinder made of insulating material and concentrically within which is located a stationary cylindrical contact member 2, there being provided an annular space between the exterior surface of contact member 2 and the interior of cylinder 1 for the passage of a compressed gas, such .as air, upwardly as indicated by the arrows when it is desired to actuate the contacts of the circuit breaker to open position.

The movable contact member of the circuit breaker is constituted by an upper cylindrical part 3 which is hollow so as to pass the switching gases and a lower part 3a of increased diameter which functions as an annular drive piston slidably fitted within cylinder 1. The lower end of the movable contact member also includes a nozzle 30 which is always closed off by the end of the stationary contact member when the contacts 2 and 3a are engaged.

Mounted on the upper end of switch cylinder 1 and secured thereto by a fitting 4 is an auxiliary cylinder 5 which includes upper and lower internal cylinder portions 512, 5b of diiferent diameters separated from one another by an internal shoulder 50. The lower, internal cylinder part 5b which has a diameter less than the internal diameter of cylinder 1 functions as a guide for a counteracting annular piston part 3b of the movable contact member, which also therefore has a diameter less than that of the main drive piston part 3a. The annular space 6 established between the two piston parts 3a, 3b is always in communication with the outside, open air by means of an aperture 7 which passes through the wall of cylinder 5. v

The upper end of cylinder 5 is closed off by a cover member 8 through which the movable contact member 3 passes in a sliding fit. Secured to the upper face of cover 8 is a cylindrical array of contact fingers 9 which are held together by a garter spring 10 so as to firmly engage the exterior surface of the movable contact member 3 as the latter slides up and down. Also secured to the upper face of corner 8 is the'exhaust duct 11 through which the switching gases are exhausted after leaving the upper exit end of the movable contact member.

The upper internal cylindrical part a serves as the cylinder for an annular damper piston 12 which normally seats upon the shoulder 50. The internal diameter of damper piston 12 is greater than that of the movable contact member so as to establish an annular passage therebetween. Accommodate in this passage is a helical spring 13, the upper end of which bears against the surface of cover 8 and the lower end of which bears against the upper face of the counteraction piston part 3b. Spring 13 biases the movable contact member 3 into engagement with the stationary contact member 2 and a similar helical spring 14 located between cover 8 and damper piston 12 serves to bias the latter to a seat on shoulder 50.

The interior 15 of cylinder 5 is connected through a wall port 16, an elbow fitting 17 and pipe 18 with a reservoir 19, for the compressed gas used to actuate the movable contact member 3, and the interior of cylinder 5 is always filled with this pressurized gas at the pressure prevailing in the reservoir 19, regardless of whether the contact members 2, 3 are engaged or disengaged.

Operation The improved circuit breaker operates in the following manner.

With the contact members in their engaged position, as shown in FIG. 1, pressurized gas from the previously mentioned reservoir is admitted into cylinder 1 through a blast valve 20 and flows upwardly. The gas pressure ap-' plied against the underface of drive piston 3a causes the latter to be raised from its seat on the end of contact member 2 and hence open the electrical circuit through the breaker which passes through contact member 2, contact member 3a, 3 and contact fingers 9.

As contact member 3a, 3 moves upward, the mouth of nozzle is uncovered and hence the switching gases created by arcing between the contact members are blown through nozzle 30 and thence upwardly through the hollow contact member 3 and discharged from the circuit breaker through exhaust duct 11. This serves to extinguish the arc in a verp effective manner and within a very short period of time.

The force acting upwardly on drive piston 3a will be determined by the pressure of the gas itself within cylinder 1 and the difference in effective surface areas of the two piston parts 3a, 3b, the former being of course greater than the latter.

During the time that the pressurized gas is flowing from the reservoir through cylinder 1, the gas pressure within cylinder 5, Le. in space 15 will decrease in the same proportion as the pressure decrease in the reservoir. Hence, there will also be a decrease in the force acting downwardly upon piston part 3b as the force acting upwardly upon piston part 3a decreases, and the two contact members will remain disengaged even in the case of a relatively great decrease in pressure in the gas reservoir.

As the movable piston part 3b moves upwardly, it compresses the biasing spring 13 and then engages damper piston 12 and effects an upward, damping movement of the latter against the counterforce of its biasing spring 14. As damper piston 12 leaves its seat on shoulder 50, it also tends to create a localized vacuum which establishes an additional suction damping eifect to thereby provide an essentially vibration-free braking for the movable contact member 3.

After the contact members of the circuit breaker have been separated and the arc extinguished, an isolating switch, not shown, but connected in series with the circuit breaker contacts in the known manner is opened to thereby isolate the load circuit controlled by the circuit breaker. After the isolating switch has been opened, the pressurized gas from the reservoir is shut off from cylinder 1 and drive piston 311 by closing the blast valve, and contact member 3 now moves downwardly as a result of the force acting upon piston part 3b. Piston part 3a is thus caused to re-engage contact member 2 and is held in pressure contact with the latter due to the continuous counter-pressure exerted upon piston part 312.

Biasing springs 13 and 14 are not relied upon to establish the contact pressure as between contact parts 2 and 3a, while they do exert some force, they are preferably made only so strong as to bring about'the starting positions for the movable contact member 2 and damper piston 12.

As shown in FIG. 2, damper piston 12 when in its uppermost position also partially covers the wall port 16. This has the advantage of providing a damping action on the contact closing stroke of contact member '3.

We claim:

1. In a circuit breaker of the gas blast type, the combination comprising a main cylinder, a pressurized gas reservoir, means including a blast valve for controlling admission of pressurized gas into said main cylinder from said reservoir, normally engaged stationary and movable contact members located within said main cylinder, said movable contact member being hollow and including at the end thereof engaged with said stationary contact member a nozzle and a drive piston part slidable within said main cylinder, an auxiliary cylinder coaxial with said main cylinder and slidably receiving a counter-acting piston part on said movable contact member, and means establishing continuous communication between said auxiliary cylinder and said pressurized gas reservoir, the effective surface area of said counter-acting piston part continuously subject to the pressurized gas in said auxiliary cylinder being less than that of said drive piston part so as to establish a force differential acting on said drive piston part in the direction to actuate said movable contact member away from said stationary contact member but only when said blast valve is opened to admit pressurized gas into said main cylinder, the force applied continuously to said counter-acting piston part serving to effect a reverse movement of said movable contact member to re-engage said stationary contact member when said blast valve is re-closed.

2. A circuit breaker as defined in claim 1 wherein said auxiliary cylinder has a stepped internal diameter established by an internal shoulder and providing two differently diametered cylinder portions, the smaller of which receives said counter-acting piston part, and a damper piston located in the other cylinder portion, said damper piston being normally seated on said internal shoulder and being engageable by said movable contact member to raise it from its seat.

3. A circuit breaker as defined in claim 2 wherein said auxiliary cylinder includes a wall port through which communication is established with said reservoir, and said damper piston is movable by said movable contact member to a position partly closing off said port.

4. A circuit breaker as defined in claim 2 and which further includes a cover member closing said auxiliary cylinder and through which said movable contact member extends, first biasing spring means located in said auxiliary cylinder between said cover member and said damper piston, and second biasing spring means located in said auxiliary cylinder between said cover member and said counter-acting piston part.

5. In a circuit breaker of the gas blast type, the combination comprising a main cylinder, a pressurized gas reservoir, means including a blast valve for controlling admission of pressurized gas into said main cylinder from said reservoir, normally engaged stationary and movable contact members located within said main cylinder, said movable contact member being hollow and including at the end thereof engaged with said stationary contact member a nozzle and a drive piston part slidable within said main cylinder, a counter-acting piston part on said mov- 1 able contact member, an auxiliary cylinder coaxial with said main cylinder, said auxiliary cylinder having a stepped internal diameter established by an internal shoulder and providing two differently diametered cylinder portions, the smaller of which receives said counter-acting piston part, a damper piston located in the other cylinder portion, said damper piston being normally seated on said internal shoulder and being engageable by said movable contact member to raise it from its seat, a cover member closing the upper end of said auxiliary cylinder and through which said movable contact member extends, first biasing spring means located in said auxiliary cylinder between said cover member and said damper piston, second biasing spring means located in said auxiliary cylinder between said cover member and said counter-acting piston part, and means establishing continuous communication between said auxiliary cylinder and said pressurized gas reservoir, the effective surface area of said counter-acting piston part continuously subject to the pressurized gas in said auxiliary cylinder being less than that of said drive piston part so as to establish a force differential acting on said drive piston part in the direction to actuate said movable contact member away from said stationary contact member but only when said blast valve is opened to admit pressurized gas into said main cylinder, the force applied continuously to said counter-acting piston part serving to eflect a reverse movement of said movable contact member to re-engage said stationary contact member when said blast valve is re-closed.

6. A circuit breaker as defined in claim 5 wherein the space defined by the interior of said cylinders and said drive and counter-acting piston parts on said movable contact member is continuously vented to the exterior of said cylinders through a cylinder wall port.

No references cited.

ROBERT K. SCHAEFER, Primary Examiner. R. S. MACON, Examiner. 

1. IN A CIRCUIT BREAKER OF THE GAS BLAST TYPE, THE COMBINATION COMPRISING A MAIN CYLINDER, A PRESSURIZED GAS RESERVOIR, MEANS INCLUDING A BLAST VALVE FOR CONTROLLING ADMISSION OF PRESSURIZED GAS INTO SAID MAIN CYLINDER FROM SAID RESERVOIR, NORMALLY ENGAGED STATIONARY AND MOVABLE CONTACT MEMBERS LOCATED WITHIN SAID MAIN CYLINDER, SAID MOVABLE CONTACT MEMBER BEING HOLLOW AND INCLUDING AT THE END THEREOF ENGAGED WITH THE STATIONARY CONTACT MEMBER A NOZZLE AND A DRIVE PISTON PART SILDABLE WITHIN SAID MAIN CYLINDER, AN AUXILIARY CYLINDER COAXIAL WITH SAID MAIN CYLINDER AND SLIDABLY RECEIVING A COUNTER-ACTING PISTON PART ON SAID MOVABLE CONTACT MEMBER, AND MEANS ESTABLISHING CONTINUOUS COMMUNICATION BETWEEN SAID AUXILIARY CYLINDER AND SAID PRESSURIZED GAS RESERVOIR, THE EFFECTIVE SURFACE AREA OF SAID COUNTER-ACTING PISTON PART CONTINUOUSLY SUBJECT TO THE PRESSURIZED GAS IN SAID AUXILIARY CYLINDER BEING LESS THAN THAT OF SAID DRIVE PISTON PART SO AS TO ESTABLISH A FORCE DIFFERENTIAL ACTING ON SAID DRIVE PISTON PART IN THE DIRECTION TO ACTUATE SAID MOVABLE CONTACT MEMBER AWAY FROM SAID STATIONARY CONTACT MEM- 